Earthquake

Earthquake images:

Earthquake description:

Weaken walls and buildings with crippling earthquakes!
Earthquake Spells cause structures to lose a portion of their hitpoints. Walls are especially vulnerable to this effect. Earthquake Spells can also cause structures that are almost destroyed to collapse instantly!

Using four or more Earthquake spell is enough to take out all the walls within the spells reach... aka Better Than Wall Breaker spell... then with haste spells or rage spells you pretty much have an instant 2 stars on any base.